FIG. 1 is a schematic structural diagram of an example of a charging apparatus in the prior art. As illustrated in FIG. 1, the charging apparatus 1 configured to charge a battery 100 includes a charging execution circuit 11, a charging protection circuit 12 and a charging control circuit 13.
Where the charging execution circuit 11 is configured to generate output voltage Vout and output current Iout at a charging output terminal thereof, and to adjust the generated output voltage Vout and output current Iout, in a period of charging.
Particularly the charging execution circuit 11 includes differential amplifiers 111 and 112, a voltage selector 113 and an adjustable switch 114 (which is a PMOS in this context merely by way of an example); and the negative input terminal of the differential amplifier 111 is a current reference input terminal of the charging execution circuit 11, the negative input terminal of the differential amplifier 112 is a voltage reference input terminal of the charging execution circuit 11, and the drain D of the PMOS 114 is the charging output terminal of the charging execution circuit 11.
The negative input terminal of the differential amplifier 111 receives an input nominal current reference Iref_s, the other positive input terminal of the differential amplifier 111 receives the output current Iout fed back at the charging output terminal of the differential amplifier 111, and the output terminal of the differential amplifier 111 outputs a control signal Ctrl_I at a positive voltage value, where the positive voltage value of the control signal Ctrl_I indicates a current difference of the output current Iout from the nominal current reference Iref_s;
The negative input terminal of the differential amplifier 112 receives an input nominal voltage reference Vref_s, the other positive input terminal of the differential amplifier 112 receives the output voltage Vout outputting by the charging output terminal of the differential amplifier 111, and the output terminal of the differential amplifier 112 outputs a control signal Ctrl_V at a positive voltage value, where the positive voltage value of the control signal Ctrl_V indicates a voltage difference of the output voltage Vout from the nominal voltage reference Vref_s;
The voltage selector 113 receives the control signal Ctrl_I and the control signal Ctrl_V, and the voltage selector 113 further receives a control signal Ctrl_P output by the charging protection circuit 12 based on a charging status signal S (e.g., a signal indicating the status of a power source Vcc0, temperature inside the charging apparatus 1, temperature inside the battery 100, etc.); and, where a positive voltage value of the control signal Ctrl_P indicates abnormality or not, and typically the positive voltage value of the control signal Ctrl_P will become higher upon abnormality; and the voltage selector 113 selects the highest one of the positive voltage values of the control signal Ctrl_I, the control signal Ctrl_V and the control signal Ctrl_P (alternatively the lowest one can be selected in a practical application for a different characteristic of an element although the highest one is selected in this context by way of an example) and sets the gate G of the PMOS 114 at the selected highest positive voltage value; and
The source S of the PMOS 114 is connected with the input power source Vcc0, and the drain D of the PMOS 114 is connected with the battery 100 and configured to generate the output current Iout and the output voltage Vout; and the conductivity between the source S and the drain D of the PMOS 114 can be adjusted with the varying positive voltage value of the gate G of the PMOS 114 to thereby adjust the output current Iout; and correspondingly since the output voltage Vout is equal to the sum of the kernel voltage V0 of the battery 100 and the voltage drop across the inner resistor R0 of the battery 100, and both the kernel voltage V0 and the voltage drop across the inner resistor R0 are dependent upon the output current Iout, so the output voltage Vout can be adjusted together with the adjustment of the output current Iout.
The charging control circuit 13 is configured to control charging to be terminated based on whether the output current Iout is lower than a nominal current reference Iref_s′.
Particularly the charging control circuit 13 includes a comparator 130. The negative input terminal of the comparator 130 receives the output current Iout fed back at the charging output terminal of the charging execution circuit 11, the other positive input terminal of the comparator 130 receives the nominal current reference Iref_s′, and the output terminal of the comparator 130 generates a charging termination signal Fin_a; and when the output current Iout is lower than the nominal current reference Iref_s′, the charging termination signal Fin_a is set at an active high level to trigger termination of charging by the charging execution circuit 11.
Where the nominal current reference Iref_s is a well-known current reference for constant-current charging, the nominal current reference Iref_s′ is a well-known current reference for termination of charging, and the nominal current reference Iref_s is higher than the nominal current reference Iref_s′; and the nominal voltage reference Vref_s is a well-known voltage reference for termination of charging.
An underlying operation principle of the existing charging apparatus 1 as illustrated in FIG. 1 will be described in details with reference to the definitions of the nominal current reference Iref_s, the nominal current reference Iref_s′ and the nominal voltage reference Vref_s. Since the charging protection circuit 12 is optional instead of being necessary, the control signal Ctrl_P output by the charging protection circuit 12 will be maintained all the time at a lower positive voltage value indicating no abnormality in the following detailed description.
In a charging start phase:
The output current Iout is far lower than the nominal current reference Iref_s, and the output voltage Vout is far lower than the nominal voltage reference Vref_s, and at this time both the control signal Ctrl_I and the control signal Ctrl_V are at lower positive voltage values so that the voltage selector 112 will also set the gate G of the PMOS 114 at a lower positive voltage value; and then since the source S of the PMOS 114 is pulled high by the input power source Vcc0, the voltage difference VGS between the gate and the source of the PMOS 114 is at a negative value and lower than the cutoff voltage of the PMOS 114 so that the PMOS 114 becomes maximally conductive and the output current Iout becomes higher;
When the output current Iout becomes higher, the positive voltage value of the control signal Ctrl_I will be higher than that of the control signal Ctrl_V, and correspondingly the gate G of the PMOS 114 will be set by the voltage selector 112 at the positive voltage value of the control signal Ctrl_I, and the conductivity of the PMOS 114 will also be controlled by the positive voltage value of the Ctrl_I; and
After some settling period of time, the conductivity of the PMOS 114 controlled by the positive voltage value of the control signal Ctrl_I will have the output current Iout maintained at the nominal current reference Iref_s, and thereafter a constant-current charging phase will commence.
In the constant-current charging phase:
The inner voltage V0 of the battery 100 will gradually become higher, and correspondingly the output voltage Vout will also gradually become higher from a lower voltage value far lower than the nominal voltage reference Vref_s; and since the positive voltage value of the control signal Ctrl_I will be maintained all the time at a positive voltage value indicating that the output current Iout reaches the nominal current reference Iref_s, the positive voltage value of the control signal Ctrl_V will be still lower than the positive voltage value of the control signal Ctrl_I as long as the output voltage Vout has not reached the nominal voltage reference Vref_s; and
When the output voltage Vout reaches and is slightly higher than the nominal voltage reference Vref_s, the positive voltage value of the control signal Ctrl_V will be higher than the positive voltage value of the control signal Ctrl_I, and then at this time the gate G of the PMOS 114 will be set by the voltage selector 112 at a higher positive voltage value of the control signal Ctrl_V so that the voltage difference VGS between the gate and the source of the PMOS 114 lower than the cutoff voltage will become higher and consequently the PMOS 114 will become less conductive and the output current Iout will become lower, and thereafter a constant-voltage charging phase will commence.
In the constant-voltage charging phase:
The output voltage Vout will be equal to the nominal voltage reference Vref_s due to a negative feedback; and
When the output voltage lout is lower than the nominal current reference Iref_s, the charging termination signal Fin_a becomes an active high level to thereby trigger termination of charging (how to trigger termination of charging will be of no interest in this context, and those skilled in the art have appreciated a number of particular implementations thereof, so a repeated description thereof will be omitted here).
Charging has been terminated so far.
As can be apparent from the description above, the charging execution circuit 11 in the existing charging apparatus 1 can be used to implement a charging scheme in which the output voltage Vout and the output current Iout is adjustable, and the charging control circuit 13 thereof can be used to control charging to be terminated, but since the charging control circuit 13 in the existing charging apparatus 1 may unreasonably control charging to be terminated and the charging execution circuit 11 thereof can not be controlled to adjust the output voltage Vout and the output current Iout, the following drawbacks may arise:
1. Whether the battery 100 has been fully charged is typically reflected by whether the kernel voltage V0 of the battery 100 reaches the nominal voltage reference Vref_s, but it is judged in the existing charging apparatus 1 when the charging termination signal Fin_a becomes active only dependent upon whether the output current Iout is lower than the nominal current reference Iref_s′ so that such a situation may occur that the output current Iout is lower than the nominal current reference Iref_s′ whereas the kernel voltage V0 of the battery 100 has been far from reaching the nominal voltage reference Vref_s, thus resulting in a drawback of insufficient charging;
2. When the kernel voltage V0 of the battery 100 has been far from reaching the nominal voltage reference Vref_s, it indicates a need for the battery 100 to be charged for a further long period of time, but the output current Iout in the existing charging apparatus 1 constantly becomes lower in the constant-voltage charging phase so that such a situation may occur that the kernel voltage V0 of the battery 100 has been far from reaching the nominal voltage reference Vref_s whereas the output current Iout is very low, thus resulting in a drawback of excessively slow charging; and
3. There may be an instantaneous up-rush of the output current Iout in the charging start phase, and alike there may also easily be an instantaneous up-rush of the output current lout in a charging restart phase after a temporary stop of charging is triggered by the control signal Ctrl_P of the charging protection circuit 12 or in a contact-again phase after the battery 100 is disconnected from the charging output terminal, so that there may easily be an impact on the input power source Vcc0 and the battery 100, thus resulting in a drawback of low reliability of charging.
Moreover there is also such a corresponding charging method in the prior art under the same principle as the charging apparatus 1 that output voltage Vout and output current Iout can be generated, and the generated output voltage Vout and output current Iout can be adjusted, in a period of charging, and charging can be controlled to be terminated based on whether the output current Iout is lower than a nominal current reference Iref_s′. Alike this charging method may unreasonably control charging to be terminated and can not control the output voltage Vout and the output current Iout to be adjusted and consequently also suffer from the drawbacks above.